[5.0.0] Fix IAM display & dismiss bugs

[jennantilla]

Description

One Line Summary

This PR addresses two In App Message bugs:

1. IAM with a custom trigger not displaying after dismissing previous IAM.
   InAppMessagesManager.attemptToShowInAppMessage: There is an IAM currently showing!
2. messageWasDismissed returning early if !_lifecycleCallback.hasSubscribers

Details

Motivation

Issue 1
Issue is reproducible following these steps:

1. Create IAM_1 that is triggered On App Open
2. Create IAM_2 that has a custom trigger
3. Run app
4. IAM_1 displays
5. Dismiss IAM_1
6. Trigger IAM_2 with addTrigger method
7. IAM_2 does not display, console logs InAppMessagesManager.attemptToShowInAppMessage: There is an IAM currently showing!

setting inAppMessageIdShowing back to null in attemptToShowInAppMessage allows IAM_2 to successfully display.

Issue 2
This issue was caught during a pair programming session where the early return would interfere with _lifecycleCallback.fireOnMain being called.

Scope

Changes affect displaying and dismissing IAMs, specifically attemptToShowInAppMessage & messageWasDismissed in InAppMessagesManager.

OPTIONAL - Other

OPTIONAL - Feel free to add any other sections or sub-sections that can explain your PR better.

Testing

Manual testing

Tested Issue 1 to ensure that second IAM successfully displays.

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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This change is 

[emawby]

If result isn't null or false that means that we are displaying a message correct? In that case setting the id to null seems wrong.